The objective of this project is to develop a new strategy to increase therapeutic efficacy in controlling recurrence and progression of cancer cells carrying the activated Ras-ERK pathway (Ras-ERK-activated cancer cells), including transitional cell carcinomas (TCCs). TCCs account for more than 90% of urinary bladder cancers (UBC), and UBC is the fifth-most common cancer in the United States. Due to an increased tendency to recur and develop to invasive cancer, TCC requires life-long surveillance, making it the most expensive cancer to manage. Although current therapies are effective in short-term treatment of TCC, long- term management is still not optimal. Growing evidence reveals that genetic alterations result in aberrantly- regulated signaling pathways, such as Ras-ERK, and upregulated mitochondrial reactive oxygen species (ROS) machinery, leading to ROS elevation in TCC cells. Drugs such as the DNA-crossing agent cisplatin are capable of inducing ROS; however, drug resistance is reportedly associated with glutathione (GSH)- dependent detoxification in chemotherapy. Our preliminary studies suggest that the histone deacetylase inhibitor FK228 has the ability to effectively induce ROS and deplete GSH by itself in Ras-ERK-activated cancer cells, including TCC cells, and to synergistically induce cell death and reduce clonogenic survival when combined with cisplatin. Thus, the rationale of this project is that it wil advance our knowledge of i) targetable, aberrantly-upregulated, ROS-generating signaling pathways induced in the course of Ras-ERK- activated cancer development and ii) combined use of Food and Drug Administration (FDA)-approved, ROS-inducing and GSH-depleting agents to effectively intervene in Ras-ERK-activated cancers. Our central hypothesis is that augmentation of ROS to a lethal level in Ras-ERK-activated cancer cells (while leaving ROS at non-lethal levels in normal counterpart cells) and reduction of GSH-dependent drug resistance will induce selective cell death to achieve highly-effective intervention of cancer with minimal side effects. To address this hypothesis, we will pursue the effectiveness of ROS-inducing and GSH-depleting agents in control of Ras-ERK-activated TCC cells in vitro and in vivo. We will also identify ROS-mediated, pro- apoptotic mechanisms of aberrantly-regulated oncogenic pathways involved in increased cell death and reduced resistance to new drug regimens. Our project is innovative with a high impact in that molecular, biochemical, cellular, and animal studies of the new combined regimens of FDA-approved agents could be efficiently translated into clinical trials to improve chemotherapy toward controlling the development and recurrence of Ras-ERK-activated TCCs and ultimately improving quality of life for patients.